Production of low cold-test oils using urea



June 9, 1959 J. s. BROWN ET Al.

PRODUCTION oF Low com-TEST 011.5 USING UREA Filed March 28, 1955 'from urea-wax adducts by heating with a wax solvent United States Patent O PRODUCTION OF LOW COLD-TEST OILS USING UREA John S. Brown, Flossmoor, Ill., and Andrew T. Jancosek, Hammond, Ind., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application March 28, 1955, Serial No. 497,235

2 Claims. (Cl. 208-25) This invention relates to the dewaxing of oils. More particularly, it relates to the treatment of wax-containing petroleum stocks to produce low cold-test oils (i.e., oils having pour points below about F.), for use as transformer oils, hydraulic oils, refrigerator oils, and the like.

Our process is an improvement in a method vof urea dewaxing, described and claimed in our prior application, Serial No. 474,549, filed December 10, 1954, employing a critical proportion of methanol and water to dewax wax-containing oils in the low cold-test range and to reduce the pour point thereof to the range of about l0 to -70 F. In our earlier process, a wax-containing stock, preferably after a preliminary solvent-dewaxing step, was subjected to contact with Iurea under adduct-forming conditions in the presence of about 0.05 to 0.5 mole of methanol per mole of urea and about 2 to 10 volume-percent of water based on the methanol. The urea and wax formed an insoluble adduct, which was readily ltered from the oil, leaving a treated oil having a pour point within the desired range. This process, as well as the present improvement thereon, is especially adapted to the treatment of wax-containing stocks in the usual viscosity range of low cold-test oils (i.e., around 40 to 300 SSU at 100 R), which ordinarily form urea adducts with difficulty and only under special conditions.

We have discovered that urea can be regenerated and recovered in exceptionally active form from urea-wax adducts, obtained inour process referred to above, by contacting the adducts with a wax solvent at a temperature between about 150 and 180 F., preferably between about 155 and 170 F. The wax is quickly liberated under these conditions and is selectively dissolved and removed by the wax solvent, while the urea is left as a finely divided solid associated with retained aqueous methanol in such a way as to. materially improve its adduct-forming properties. We have also discovered that such regenerated urea (or urea that has been preconditioned by treatment with aqueous methanol under similar conditions) forms urea-,wax adducts from wax-containing 4oils in the low cold-test range more promptly, rapidly, and consistently than fresh or untreated urea, and with a substantially shorter induction period.

It is accordingly an object of our invention to provide an improved method of urea-dewaxing applicable to the treatment of Wax-containing stocks in the viscosity range of vlow cold-test oils. Another object is to improve the effectiveness of adduct formation between urea and waxes. Another object is to improve the urea dewaxing i of hydrocarbon oils in a cyclic process. These and other objects of our invention will be apparent from the following description and the appended claims.

In one aspect, our invention lies in regenerating urea a temperature between about 150 and 180iv F.

In another aspect, our invention lies in preconditioning urea for adduct formation with waxes by heat-treat- -ment at `150 to 180 F. with an inert hydrocarbon liquid 2,890,161 Patented June 9, 1959 BCC in the presence of aqueous methanol in our defined optimum range.

In a simple embodiment of our invention, a wax-containing charging stock is commingled with active, regenerated urea, optionally with added aqueous methanol and a diluent hydrocarbon liquid, and the mixture is a'gitated at ordinary temperature, whereupon an insoluble waxurea adduct forms and reaches substantial completion in about 30 to 60 minutes. The resulting slurry is filtered by conventional means, suitably through an ordinary canvas filter, air pressure being used as needed to speed the filtration. The diluent liquid serves to reduce the viscosity of the reaction mixture and to minimize retention of charging stock on the adduct. If no diluent is used in the reaction mixture, up to around 10 percent of the dewaxed oil is ordinarily retained on the adduct, and can be removed if desired by washing with diluent liquid, e.g., half a volume of a light naphtha, based on the charging stock. The filtrate and washings are combined and stripped of diluent to give the desired low cold-test product oil. Any dissolved methanol is simultaneously removed, and can be recovered from the stripper distillate. The wax-urea adduct is slurried with a wax solvent, such as an additional quantity of the diluent liquid, and is heated to a temperature between about 150 F. and 180 F., preferably between about 155 and 170 F. The adduct is decomposed in this treatment practically as soon as the desired temperature is reached, but we generally maintain the temperature at the desired level for a period of 0.1 hour or more, preferably between about 0.5 and l hour. The liberated wax dissolves in the wax solvent. The urea is simultaneously regenerated in the form of a finely divided solid, intimately associated Awith aqueous methanol in an activating proportion. The regenerated urea is separated from the resulting slurry by filtration, centrifugation, or the like, and is thereby recovered in a form suitable for immediate reuse in the treatment of additional charging stock. The wax is recoverable from the break-oil solution by stripping.

The formation of an adduct between preconditioned urea and waxy normal parains proceeds at any temperature below about 130 F. Ordinary temperatures in the range of about to 80 F. are preferred. Temperatures above 100 F. are less satisfactory, because the adducts become progressively less stable at higher temperatures; and temperatures below about 50 F. may be less -satisfactory because of contacting and filtering difficulties arising from increased viscosity of the reaction mixture.

The ratio of urea to charging stock in our process varies considerably, depending upon the wax content of the stock. Ordinarily, about 4 pounds of urea are sufficient to effect substantially complete removal of 1 pound of wax. For example, a propane-dewaxed Mid-Continent SAE 10 oil, which ordinarily contains approximately 0.4 pound of adductible material per gallon, requires at least about 1.6 pounds of urea per gallon of oil for best results. A smaller urearwax ratio gives incomplete wax removal and less than the maximuml pour point lowering. We prefer to contact urea and charging stock in the proportion of around 4 to 8 pounds of free urea per pound of adductible wax contained in the stock.

The activation or preconditioning of ureain our process employs methanol and water in a volume ratio between about :10 and 98:2 and in the proportion of about .0.5 to 4 gallonsper hundred pounds of urea. We `prefer to employ aqueous 94 to 9.7 percent methanol inthe proportion of aroundl to 2 gallons per hundred pounds ,ofurea l In the treatment of high-viscosity oils and/orI high-wax stock s, ditliculty may be encountered in -agitating-and 'filtering the reaction slurry. In such-cases, ardiluent liquid, such as a naphtha or an alkylate, is added to the charging stock to thin the mixture. This results in better contact between the urea and oil as well as more rapid ltering. The quantity of diluent to be used in any case will `depend upon the viscosity of the charging stock, the wax content thereof, the mixing eiciency of the equipment, and the desired ltration rate. It is of course desirable to use diluents in as low a concentration as possible in order to minimize the difliculty and expense of recovery thereof. We have found that diluents can conveniently and advantageously be employed in many cases in proportions up to 200 percent or more based on the charging-stock oil, depending largely upon the viscosity thereof. When a diluent is indicated, we prefer to employ between about 50 and l0() percent thereof, based on the charging stock. Many hydrocarbon liquids are suitable for this purpose so long as they are substantially wax-free, although it will be apparent that the results obtained therefrom are not necessarily equivalent. We have successfully employed naphthas and other hydrocarbons, including pentane, isopentane, isooctane, benzene, toluene, light alkylate, heavy alkylate, and the like. Liquids of the same class are suitable for use in the adduct-decomposition step.

In an advantageous embodiment of our process employing a diluent liquid, we use the same diluent in both adducting and regenerating or preconditioning the urea. For this purpose, it is desirable to choose a liquid which is inert to urea at all temperatures and which does not boil at the temperatures and under the conditions ernployed in adduct decomposition. Our preferred diluent is a light aviation alkylate, obtained by copolymerization of a mixed butylene stream. This material is inert to urea at all temperatures (as contrasted with pentane, which forms an adduct at F. and lower), and has a iinal boiling point around 350 F. A desirable alkylate fraction has a boiling range of about 200 to 350 F. This material is readily stripped from the dewaxed charging stock, leaving a treated material free from extraneous substances.

Another advantageous diluent is a heavy alkylate, obtained for example as a bottoms fraction from the production of isooctane by alkylation. This material is also inert to urea at all temperatures, and has an initial boiling point of 350 F. A desirable heavy alkylate fraction has a boiling range of about 350 to 800 F. Heavy alkylate is a clean material which does not affect the reactivity of the urea and does not adversely affect the urea-treated oil. It is therefore unnecessary to wash this material out of the urea, or to strip it completely out of the treated oil. It is necessary only to strip the oil to the desired ash point. Any alkylate remaining therein is highly branched, and is beneficial rather than detrimental to the treated oil. Moreover, when the adducts have been broken by heating with alkylate, it is unnecessary to strip the alkylate from the resulting wax solution unless the wax is desired as a separate product. The wax-alkylate solution can b e sent directly to catalytic cracking, if desired, where full value for the alkylate will be realized, and the wax will be cracked to desirable products.

In a preferred embodiment of our process, the decomposition of the urea adducts is carried out by heat treatment in the presence of an additional quantity of the partially dewaxed charging stock as a break oil. In this embodiment, the urea-wax adducts are dispersed in a further quantity of the charging stock, suicient to form a fluid slurry with the adducts and to dissolve the waxes contained therein, and the resulting slurry is heated to the required temperature for decomposing the adducts and releasing the waxes and urea, as set forth hereinabove. The waxes are dissolved by the charging-stock liquid, and the wax-oil solution is separated from the regenerated urea by ltration, centrifugation, settling and deeantation, or the like. Surprisingly, the pour point of the wax-enriched oil obtained thfcby iS Practically fh@ same as the charging-stock oil, and as `a result the said oil can be returned to the refinery pool of partially dewaxed oils without detriment to the latter. Thus, this embodiment of the process can be visualized as a means for transferring the wax from a portion (e.g., 20 to 50 volume-percent) of a low-wax oil pool to the remainder of the pool, yielding a quantity of low cold-test oil while avoiding any substantial eect on the properties of the remainder of the pool. This advantageous result is feasible apparently because the removal of the last traces of wax from the oil produces a very large decrease in the pour point thereof, while adding the same amount of wax to the charging stock has practically no effect in raising its pour point.

The attached drawing illustrates an embodiment of our invention in which a propane-dewaxed Mid-Continent SAE 5 distillate is continuously contacted with preconditioned urea, the reaction slurry is ltered to separate the resulting urea-wax adducts from the dewaxed oil, the dewaxed oil is stripped of low boilers to produce a low cold-test oil of the desired flash point, the urea adducts are decomposed by heating with additional charging stock or other suitable break oil, and the regenerated and preconditioned `urea is employed to dewax a further quantity of the charging stock.

In the drawing, the charging stock, supplied through line 11, is commingled in mixing tank 12 with preconditioned urea, supplied by recycle through line 13, makeup aqueous methanol as desired, supplied through line 14, and a diluent such as light aviation alkylate, supplied by line 15. The mixture emerges through line 16 to pump 17, and is conveyed through line 18 into the bottom of reactor 19, a vertically elongated vessel separated into vertically disposed compartments (eg. 20) by means of horizontal baffles (e.g. 21). Each of the compartments is supplied with agitating means (eg. 22). Urea adduct formation reaches substantial completion in 20 to 30 minutes, at the end of which time the reaction product emerges from the top of the reactor and flows through line 23 into the top of methanol stripper 24. A quantity (or `further quantity) of diluent liquid is supplied if desired through line 25. The stripper is suitably operated at an absolute pressure around 75 to 100 mm. Hg. The reaction product flows downward over packing material 26, and emerges from the bottom of the stripper through line 27 into pump 28, from which it is recycled in part through line 29, valved line 30, heater 31, and line 23, the temperature being maintained at a stripping level between about and 115 F. in this way. Methanol and water are taken off overhead as a vapor stream and are condensed in cooler 32. The condensate ows to receiver 33, and is taken off through line 34 for recycle. The receiver is connected through line 35 to a suitable vacuum source.

The stripped reaction slurry flows through valved line 36 into continuous drum iilter 37. The ltrate therefrom ows through line 38, pump 39, polishing filter 40, and heater 41 into ilash drum 4,2, operated at around 230 F. and approximately atmospheric pressure. A substantial proportion of the diluent liquid volatilizes in the ash drum, and is taken olf through line 43 to condenser 44. The liquid stream from the ash drum flows through line 45 into an upper portion of stripper column 46, and is stripped therein with steam, introduced through line 47 into a lower portion of the column. The product oil is dried by heating means 48 at the bottom of the stripper column, and emerges through cooler 49 to storage. The overhead vapor stream, consisting largely of diluent liquid and water, ows through line 50 and line 43 into cooler 44, and the condensate is led into decanter 51,. The aqueous lower) phase in decanter 51 is withdrawn through line 52 and discarded. The organic (upper) phase is reluxed in part through valved line 53 to the top of stripper 46.

The filter cake in continuous filter 37 is washed with a suitable liquid (e.g., light aviation alkylate) and supplied through line 54, and is removed by doctor blade 55 to receiver 56, where it is slurried with a suitable break oil, such as an additional quantity of the charging stock, supplied at elevated temperature through heater 57 and valved line 58. The resulting slurry is transferred by pump 59 through line 60` and line 61 to an agitated decomposer vessel 62, additional hot break oil being added as desired through valved line 61. Makeup urea is also added to vessel 62 in order to give it a preliminary activating or preconditioning treatment in the presence of a small residual proportion of aqueous methanol under adduct-decomposing conditions before it is used to contact fresh charging stock. Additional aqueous methanol may be added to the decomposer if desired. Within the decomposer 62, the temperature is maintained at a level between about 150 and 180 F. Under these conditions, the urea adducts are broken apart, and the liberated waxes are dissolved by the break oil, while the urea is regenerated in solid, finely divided form, retaining an activating quantity of methanol and water. The resulting slurry is transferred by pump 63 through suitable lines into continuous filter 64, where the regenerated urea is washed with (for example) light aviation alkylate, and is withdrawn to urea hopper 65 for recycle.

The filtrate from filter 64, consisting largely of break oil, wax, and wash liquid, emerges through line 66 and is led through heater 67 into an upper section of stripper column 68. Within the column, the wash liquid and any other low boilers are stripped out with steam, introduced through line 69 into a lower section of the column, and emerge overhead through line 70 and condenser 44 to decanter 51. A portion of the organic phase from decanter 51 is refiuxed to the top of stripper column 68 through valved line 71, and another portion is withdrawn through valved line 72 to recycle as diluent liquid. The bottoms from stripper 68 are dried by heating means 73, and emerge through cooler 74. This material consists largely of break oil plus wax. It can be returned to the partially dewaxed oil pool, if desired, or can be sent to catalytic cracking.

Our invention will be more Ifully understood from the following specific examples.

Example 1 The following tests illustrate the effectiveness of lowtemperature adduct decomposition according to our new process in producing regenerated urea of high activity, requiring no further addition of methanol or other activator for subsequent adduct formation with waxes.

I. Dewaxing.-A propane-dewaxed SAE 5 lube-oil charging stock having a pour point of F. was dewaxed according to the following procedure: A 32-pound portion of the charging stock Was commingled with 8 pounds 4i of -fresh urea and 600 milliliters of aqueous 97 percent methanol, and the mixture was agitated at ambient temperature for 45 minutes. The reaction product was filtered, and yielded 21.5 pounds of dewaxed oil having a pour point of 30 F.

II. Urea regeneraton.-The solids from Test I, consisting essentially of urea-wax adducts, unreacted urea, and retained oil, were reslurried with 26 pounds of fresh charging stock, and the slurry was heated with agitation to 180 F., then filtered hot. The filtrate weighed 33 pounds, and had a pour of 0 F., unchanged.

III. Dewaxing.-The regenerated urea obtained in Test II was reslurried without added methanol with 33.5 pounds of fresh charging stock, and the slurry was agitated at ambient temperature for 45 minutes. On filtration, 27 pounds of dewaxed oil were obtained having a pour point of -30 F.

IV. Urea regeneration-The solids obtained in Test III were reslurried, agitated, and heated to 174 F. with 28 pounds of fresh charging stock. The treated slurry was filtered hot, and 32.5 pounds of filtrate were obtained having a pour point of 0 F., unchanged.

V. Dewaxng.-The regenerated urea from Test IV was contacted with 32.25 pounds of fresh charging stock under adduct-forming conditions, as outlined above, without additional methanol, and 18 pounds of treated oil were obtained having a pour point of 25 F.

VI. Urea regenerat0n.-The solids obtained in Test V were reslurried, agitated, and heated to 180 F. with 32 pounds of fresh charging stock, then filtered hot. The rcovered stock weighed 46 pounds and had a pour point o 5 F.

VII. Dewaxng.-The regenerated ureafrom Test VI was contacted with 34 pounds of fresh charging stock under adduct-forming conditions, without added methanol, and 30 pounds of dewaxed oil were obtained having a pour point of -25 F.

Example 2 The following tests illustrate the superior results obtained `with regenerated urea in the dewaxing of an SAE 10 stock, as compared with 'fresh urea.

A series of tests were carried out, in each of which 8 pounds of fresh urea were commingled with 1.5 pounds of aqueous 97 percent methanol and 36 pounds of propane-dewaxed SAE 10 lube-oil stock having a pour point of 0 F., and the resulting slurry was agitated at ambient temperature for 75 minutes, then filtered. The treated oils were found to have pour points ranging from 0 F. to -35 F., indicating that urea-wax adduct formation had taken place inconsistently, and in some cases not at all.

The crude adducts obtained in the above tests were separately decomposed by agitating and heating to 170 F. with fresh 25-pound portions of the SAE 10 charging stock and filtering while hot to separate the regenerated urea. Each of the individual portions of regenerated urea `were then contacted under adduct-forming conditions, without additional methanol, with fresh 36-pound portions of the SAE 10 charging stock under the conditions set forth above, and treated oils were obtained in each case having pour points in the range of -25 to 35 F.

Example 3 The following tests illustrate the shorter induction time encountered in dewaxing an SAE 10 stock with regenerated urea, as compared with fresh urea..

A series of four tests were made, in each of which 2,470 grams of propane-dewaxed SAE 10 lube-oil stock having a pour point of 0 F. were commingled with 500 grams of fresh urea land 42 milliliters of aqueous 97.5 percent methanol and agitated at F. until urea-wax adduct formation had reached substantial completion. In each test, a sample of the reaction mixture was withdrawn from time to time, and the pour point of the oil was determined as a measure of the extent of urea-wax adduct formation.

For comparison, a series of four similar tests were made with urea that had been regenerated from urea-wax adducts in accordance with our invention.

The induction times and the times required for complete adduction are given in the table below. The superiority of regenerated urea is apparent from these data.

Our invention is effective in treating wax-containing hydrocarbon oils ranging in viscosity from about 40 to 300 SSU at 100 F. andrin pour point from about O to 100 F. These viscosities and pour points correspond in general to the SAE 10, SAE 5, and lighter grades. Our process can be used, for example, to treat a mineral seal oil of 45 SSU viscosity at 100 F. and pour point around 35 F., and to obtain therefrom `a treated oil having a pour point of -70 F., which is suticiently low for most uses. The minimum pour point attainable appears to depend on the nominal viscosity of the oil, varying directly as a logarithmic function thereof. A previous solvent-dewaxing of the stock, in some cases, also affects the pour point obtainable by urea dewaxing according to our technique. Oils having viscosities of 40 to 150 SSU at 100 F. urea-dewaxto the same low pour point whether previously dewaxed or not. In the viscosity range of 150-200 SSU, urea dewaxing produces oils of low pour point only from oils which have been previously dewaxed by other means-eg., by propane dewaxing, cold pressing, or the like. From 200 to 300 SSU, urea forms adducts with the waxes in both distillates (undewaxed) and cold-pressed oils, but the improvements in pour point are not as great. Urea dewaxing also tends to increase the viscosity of the treated oil, ordinarily up to about 10 percent.

While we have described our invention with reference to certain specic embodiments thereof, it is to be understood that such embodiments are illustrative only and not by wvay of limitation. Numerous modifications and equivalents of the invention will be apparent to those skilled in the art from our description and from the appended claims.

In accordance with the `foregoing description, we claim as our invention:

1. In a cyclic process for treating a wax-containing hydrocarbon oil of not greater than SAE 10 viscosity and pour point above F. and obtaining a low cold-test oil therefrom, wherein said wax-containing oil is contacted with urea in a proportion of at least about 4 pounds of solid urea per pound of wax contained in said oil in the presence of a liquid alkylate fraction and between about 0.5 and 4 gallons of aqueous methanol per 100 pounds of urea, said methanol containing between about 2 and 10 percent by volume of water, said contacting is continued under conditions and for a sufficient time to form urea adducts with the straight-chain waxes contained in said oil, said adducts and any unreacted urea are separated from the resulting slurry, said liquid alkylate fraction is stripped from the treated liquid resulting therefrom, whereby the desired low cold-test oil is obtained having a pour point substantially below 0 F., said urea adducts are decomposed by contact with a quantity of said liquid alkylate fraction at elevated temperature below the melting point of urea, whereby said straight-chain waxes are liberated and dissolved in said alkylate fraction and urea is regenerated in solid form, and said regenerated urea is recovered and used to contact additional charging stock, the improvement which comprises retaining activating proportions of methanol and Water on the regenerated urea by decomposing the urea adducts in the presence of a liquid alkylate fraction and at a temperature between about 155 and 170 F., said temperature being above the decomposition temperature of the urea adducts and below the liberation temperature of the retained methanol and water, and regenerating the urea in a nely divided highly active form for treating additional charging stock with said activating proportions of methanol and water retained on the urea.

2. In a cyclic process for treating a wax-containing hydrocarbon oil having a viscosity Ibetween about 40 and 300 SSU at F. and pour point above 0 F. and obtaining a low cold-test oil therefrom, wherein said waxcontaining oil is contacted with urea in a proportion of at least about 4 pounds of solid urea per pound of wax contained in said oil in the presence of a liquid alkylate Yfraction and between about 1 and 2 gallons of aqueous methanol per 100 pounds of urea, said methanol containing between about 3 and 6 percent lby volume of water, said contacting is continued under conditions and for a suicient time to form urea adducts with the straight-chain waxes contained in said oil, said adducts and any unreacted urea are separated from the resulting slurry, said liquid alkylate fraction is stripped from the treated liquid resulting therefrom, whereby the desired low cold-test oil is obtained having a pour point substantially below 0 F., said urea adducts are decomposed by contact with a quantity of said liquid alkylate fraction at elevated temperature below the melting point of urea, whereby said straightchain waxes are liberated and dissolved in said alkylate fraction and urea is regenerated in solid form, and said regenerated urea is recovered and used to Contact additional charging stock, the improvement which comprises retaining activating proportions of methanol and water on the regenerated urea by decomposing the urea adducts in the presence of a liquid alkylate fraction and at a temperature between about and 170 F., said temperature being above the decomposition temperature of the urea adducts, above the liberation temperature for said waxes, and below the liberation temperature of the retained methanol and water, regenerating the urea in a nely divided highly active form for treating additional charging stock with said activating proportions of methanol and water retained on the urea, and cyclically repeating the steps of urea-adduct formation and decomposition with the regenerated urea without addition of further quantities of methanol and water thereto.

References Cited in the le of this patent UNITED STATES PATENTS 2,518,677 Garner et al Aug. l5, 1950 2,549,372 Fetterly Apr. 17, 1951 2,578,054 Fetterly Dec. 11, 1951 2,634,261 Fetterly Apr. 7, 1953 2,661,317 Skelton et al. Dec. 1, 1953 2,681,335 Gorin June 15, 1954 2,700,664 Weedman et al Ian. 25, 1955 2,731,455 Salzman et al Jan. 17, 1956 2,731,456 Weedman Jan. 17, 1956 UNTTED STATES PATENT @FFICE CERTIFCATE GF CORRECTION Patent No., 2,890,161 June 9, 1959 John S Brown et al It is herebT certified that error appears in the -printed specification of' the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 36, for "3500 F., 'f read m 3400 F., 7; oolumrl 5, line 66, for "and had a pour of O0 F." read and had a pbllr point of O0 Fu e Signed and sealed this 3rd day of November 195%i (SEAL) Attest:

RUBERT C. WATSON KARL H@ XLINE Commissioner of Patents Attesting @fficer 

1. IN A CYCLIC PROCESS FOR TREATING A WAX-CONTAINING HYDROCARBON OIL OF NOT GREATER THAN SAE 10 VISCOSITY AND POUR POINT ABOVE 0*F. AND OBTAINING A LOW COLD-TEST OIL THERFROM, WHEREIN SAID WAX-CONTAINING OIL IS CANTACTED WITH UREA IN A PROPORTION OF AT LEAST ABOUT 4 POUNDS OF SOILD UREA PER POUND OF WAX CONTAINED IN SAID OIL IN THE PRESENCE OF A LIQUID ALKYLATE FRACTION AND BETWEEN ABOUT 0.5 AND 4 GALLONS OF AQUEOUS METHANOL PER 100 POUNDS OF UREA, SAID METHANOL CONTAINING BETWEEN ABOUT 2 AND 10 PERCENT BY VOLUME OF WATER, SAID CONTACTING IS CONTAINED UNDER CONDITIONS AND FOR A SUFFICIENT TIME TO FORM UREA ADDUCTS WITH THE STRAIGHT-CHAIN WAXES CONTAINED IN SAID OIL, SAID ADDUCTS AND ANY UNREACTED UREA ARE SEPARATED FROM THE RESULTING SLURRY, SAID LIQUID ALKYLATE FRACTION IS STRIPPED FROM THE TREATED LIQUID RESULTING THEREFROM, WHEREBY THE DESIRED LOW COLD-TEST OIL OBTAINED HAVING A POUR POINT SUBSTANTIALLY BELOW 0*F., SAID UREA ADDUCTS ARE DECOMPOSED BY CONTACT WITH A QUANTITY OF SAID LIQUID 